Common silicate glasses are among the most brittle of the materials. However, on warming beyond the glass transition temperature Tg glass transforms into one of the most plastic known materials. Bulk metallic glasses exhibit similar phenomenology, indicating that it rests on the disordered structure instead on the nature of the chemical bonds. The micromechanics of a solid with bulk amorphous structure is examined in order to determine the most basic conditions the system must satisfy to be able of plastic flow. The equations for the macroscopic flow, consistent with the constrictions imposed at the atomic scale, prove that a randomly structured bulk material must be either a brittle solid or a liquid, but not a ductile solid. The theory permits to identify a single parameter determining the difference between the brittle solid and the liquid. However, the system is able of perfect ductility if the plastic flow proceeds in two dimensional plane layers that concentrate the strain. Insight is gained on the nature of the glass transition, and the phase occurring between glass transition and melting.

Electron correlation microscopy (ECM) is a new technique that utilizes time-resolved coherent electron nanodiffraction to study dynamic atomic rearrangements in materials. It is the electron scattering equivalent of photon correlation spectroscopy with the added advantage of nanometer-scale spatial resolution. We have applied ECM to a Pd40Ni40P20 metallic glass, heated inside a scanning transmission electron microscope into a supercooled liquid to measure the structural relaxation time τ between the glass transition temperature Tg and the crystallization temperature, Tx. τ determined from the mean diffraction intensity autocorrelation function g2(t) decreases with temperature following an Arrhenius relationship between Tg and Tg+25 K, and then increases as temperature approaches Tx. The distribution of τ determined from the g2(t) of single speckles is broad and changes significantly with temperature.

(Cu0.47Zr0.45Al0.08)100–xDyx (x = 0, 1, 2, 3, 4; at.%) metallic glasses with greatly enhanced glass-forming ability (GFA) and plasticity were synthesized based on microalloying technique. The structure, thermal stability, and elastic properties of the BMG samples were studied by x-ray diffraction (XRD), differential scanning calorimetry (DSC), and ultrasonic measurements, respectively. With addition of minor dysprosium (Dy), fully metallic glassy rods with diameters exceeding 20 mm could be successfully fabricated by copper mold casting. In addition, the Cu–Zr–Al–Dy BMGs exhibit good mechanical properties under a compressive deformation mode, i.e., high yield strength of 1735–1906 MPa, Young's modulus of 85–100 GPa, and distinct plastic strain up to 4.02%. The strength and plasticity show remarkable correlations with glass transition temperature and Poisson's ratio, respectively. The role of minor Dy addition in enhancement in GFA and mechanical property of the Cu-rich BMGs is also discussed.

A hard magnetic Nd50Al15Fe15Co20 bulk metallic glass (BMG) was prepared in the shape of a rod up to 3 mm in diameter by suction casting. The glass transition and crystallization behaviors as well as their kinetic nature have been studied. In contrast to the previously reported hard magnetic Nd–Al–Fe–Co BMGs, Nd50Al15Fe15Co20 as-cast rod exhibits a distinct glass transition and multistep crystallization behaviors in the differential scanning calorimetry traces and lower coercivity. The BMG provides an ideal model for the investigation of glass transition and crystallization of hard magnetic Nd–Al–Fe–Co glass-forming alloys.